Fluid pressure actuated motors



United States Patent [72] Inventor Richard Thomas Fowler Tyseley, England [211 App]. No. 780,415 [22] Filed Dec. 2, 1968 [45] Patented 15, 1970 [73] Assignee Girling Limited Birmingham, England [32] Priority Dec. 22, 1967 [33] Great Britain [31 No. 58,495/67 [54] FLUID PRESSURE ACTUATED MOTORS 4 Claims, 2 Drawing Figs.

[52] U.S.CI.....:.'I 92/63 [51] lnt.Cl FOlb 7/00 [50] Field of Search 92/64, 63, 49,61,62, 107, 165; 188/182.02

[56] References Cited UNITED STATES PATENTS 2,726,738 12/1955 Fawick 188/152 3,090,359 5/1963 Hoppenstand 92/64X 3,152,518 10/1964 Ayers 92/49X Hlill Primary E.taminerMartin P. Schwadron Assistant ExaminerLeslie J. Payne Attorney-Holcombe, Wetherill & Brisebois ABSTRACT: In a fluid pressure motor having at least two pistons working in separate cylinder spaces and coupled together in tandem, the cylinder space in which one piston works overlaps axially with the cylinder space in which an adjacent piston works. In the construction described and illustrated there are two pistons each formed as a metal pressing and including an annular skirt which throughout the working stroke of the piston is in engagement with a stationary seal carried by the wall of the cylinder in which that piston works; each piston is of dished form towards one end of its cylinder and the wall at that end of the cylinder is complementarily shaped; the opposite end wall of one cylinder provides an abutment for a coil compression spring which bears against the piston in that cylinder and is accommodated within the dished recess of the piston.

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in a preferredfo'rm'of motor in accordance with the inven- "the psn lix andito thepressure c cylinder spaces and mechanically interconnected intandem to apply their-working outputs to a common output member. A motor of this type has the-advantage over'a conventional single piston motor that the overall diameter-can be considerably reduced for a given output at a given applied'fluid pressure.

lnaccordance \vitlt the present invention the cylinder space in which one piston of subtle motorworks'overlaps axially with the cylinder, space in which an-adjacent piston works, thus allowing thexoverall axial length-of the motor to be tion one (at least) o f the' pistons is formed as'a metal pressing and includes a peripheral skirt which throughout the working stroke'of the pistonisin'engagerrien't with astationary seal 'ca'rried by'the wall of the cylinder in which that.pis'ton works, this skirt (when thepji'stonis atone end of its stroke) surrounding jacent piston works;

at least partof the length ofthecylinder'space'in which an ad- These and otherfeatures andadvantagesf of the inventionare exemplifiedinthe constructional form of the invention which will now be described, byway of example only, with reference to'the' accompanying dr'awin'gs, -in which:

l G. l is an'axial cross section of a motor in accordance with the invention, an a FIG, 2 l a scrap cross sectiontak'en. in another axial plane to illustrate'a detail.

The inotor'uriiticomprises a generally cylindrical, open "ended body' portion 10, having a central-dividing wall 12 which, together with'a pair of cylinder 'end closures l4 and 16, forms a forward andfarear motor compartmentor cylinder space. .A 'pairoffpresse'd ,jsteel pistons 18 and are located one in'each of the motor compartments to divide the compartments into atmospheric chambers 2 2 'alncl 24 in frontof'the respective,pistonsfandpressure chambers and 28 to the 1 rear of the re pective pistons.

The dividingwallilZ'has a central. aperture 23'which sealingly and slidably" receives the forward end of a stem, 29 forming part ofa pressure member ',whic'h is housed within the chamber 24' and has. an nlargeddi'sc-shaped rear end portion 32,;which is in abutting engagementwith'the piston 20. A thtust'pad-Jd'is welded to the back face of'fthje 'piston' ls and is provided with eompleinentary abutment surfacesfor the partthe piston 20, and the'dividing wall'lZhas a peripheral skirt 64, the interior surface 68 of which forms the forward'part of the rear cylinder space. The outersurface'of the skirt 64 is spaced from the interior surface 66 of-the forward pressure chamber 26, sufficiently to facilitate machining of the surface 66 and to receive'a rearwardly extending's'kirt on the'forward piston v18.. The pistons l8 and 20 are? Sealed by respective piston seals 70 and 72 mounted in the l0.

Bothpistons; l8 and 20 are formed asmetal pressings which.

are each dished rearwardly so as to have a flat'central portion or web, located axially between the forward and rear extremities of the piston. The piston returnspring 52is located within the dished part of piston 18, so that whenthe piston is fully forward, the spring is accommodated wholly within the piston 18 and does not interfere with the 'workingstr'oke of the piston The rear walls 12 and 16 of the 'pres'sure'chambers 26-and 28 are shaped to conform substantially tothe adjacent pistons,

so asto reduceas far sa practically-possible-the minimum volume of the chambers 26 and 28 when the, motor is in its unactuated condition, as drawn. This arrangement reduces to a minimum any delaybetween the introduction of fluid pressure into the chambers 26 and 28 and initial forward displacement of the pistons. 1

In operation, the delivery of pressuriz'edt'luid such as compressed air to the chambers 26'and 28 produces a pressure difference across the pistons 18 and 20, which rnove in opposition to the retumspring 52 and displace the' push rod 42 outwardly throughthe end'closure14,.during-which stage air in the chambers 22 and 24 is exhausted to atmosphere through the opening 40 and ports 60 and 61 respectively. The push rod (which may, for examplebe connected. to-a'. brake-applying mechanism) transmits a force which is equal to the sum of the force outputs of the two pistons. I

. When-the pressure in .chambers 26 and 28 is relieved, the

pistons are returned totheir rest position under the action of the return spring 52, atmospheric air being drawn back into the chambers 22 and 24.

spherical jend dfi ofthe' stem 29 and for'a'frustoconical seating 38xmachined, into the. front end of theidividirig wall 12 around- The end wall l4 hasacen tral aperture 4ll'which receives with substantial clearance a push rod .42, whose rear end rests in a spherical seatingbn a force transmitting element 44, to i which his connected by apin 46 passing through a diametrical hole 48 adjacent the push rod end. The element 44 includes an enlarged disc-shaped rear end portion 50 which abuts the l piston 18. A piston return coil spring 52,'loca'ted between the end closure 14 and the element 44,'acts tokurge the piston- 18 against theabutment 38 and the piston 20 against a rubber or like buffer 54, on thefront face of th'e'end closure 16. The

motor is adapted for-attachment, e.gL tea-vehicle frame, by a set of l'tlOlllltlllgbQltSjS carried by the end closure 14. r

Fluid under. pressure" is" introduced -.into the pressure The motor unit may advantageously befuseld in conjunction with a dual 'brakesystem in which:theiinletsjfiand 58 are "each connected to separate pressure sources such that failure of one source of supply will not cause aeom'plete failure.

lf-the supply to the rear cylinder fails,the.forward piston 18 can move forwardly on itsown, leaving the rear-piston behind (since the pistons make abutting engagement only and are not secured to each other); if the supply to theforward cylinder fails, the rear piston can move forwardly,'pushi ng the forward piston ahead of it.

The motor has been described as being operated by superatmosphericair pressure, but could obviouslybemodified so as to be vacuum operated(either'air or; vacuum suspended) or hydraulically operated. A motor in accordancewith the inven--x tion could also be used in conjunction with arrangements other than braking systems.

lclaimb 1. A fluid pressure motor comprising a'body defining first and second coaxial cylinder spacess'eparated, from one chamber 26 by way of aradial port 57 in :the body-portion l0,

hamber 28through an axial port 58in the endclosurelfifli- 1 Thechamber 2'4fis:conriectedto atmosphere by means ofa a spaced radially inward from, said first cylinder space, first and second pistons-respectively working in said. cylinder spaces,

plurality ,ofport means, eachuof the general form shown in FlCuZ and'comprising'a' radial port 60 communicating'with an axial port 61. niialom rend; the port 60 is provided with an apertured' end cap 62'forcarrying an air filterielement (not shown). The" chamber the aperture 40; '1

221isconnted toatrrrosphere through another by a dividing wall so'shaped that-the first cylinder space located on one side of said wall includesan annular end portion which encircles the adjacent-end portion of the second cylinder space located-on the other, side of said wall and each piston dividing its cylinder space, into two-fluid chamgageable in said annular end portion,- s'aid second piston engagingthe dividing wall in a second end portion formed by said wall so that said second end portion is radially inwardly arranged with respect to said first annular portion and means of its stroke being accommodated within the dishing when the piston is at the other end of its stroke.'. r f y 4. A fluid pressure motor as defined-in claim 1 in which at least one piston' is formed as a metal pressing which is dished, one end wall of the cylinder space in which that piston works being complementarily shaped so as to reduce as far as possible the minimum volume of the chamber formed between the piston and that end wall. 

